1. Field of the Invention
This invention relates to a medical apparatus for placing a coil assembly at a preselected position within a vessel of the human body, and more particularly, relates to a deployment catheter having a distal section for retaining and transporting the coil assembly within the vessel and having a control mechanism for releasing the coil assembly at the preselected position. This apparatus is particularly suited for transporting the coil assembly through the tortuous vasculature of the human brain and releasing the coil assembly within an aneurysm.
2. Description of the Prior Art
For many years physicians have been placing various devices within a blood vessel of the human body in order to treat an aneurysm or to occlude a vessel. Such devices are placed within the aneurysm or vessel using one of several catheter deployment systems. These deployment systems transport and release devices at a particular location within the vessel. The combination of different devices and deployment systems provide physicians with reliable methods of treating aneurysms.
Various types of devices are placed within an aneurysm or a vessel to occlude the flow of blood by promoting thrombus formation. Such devices include dilatation balloons, radiopaque fluids, liquid medications, and embolic coils. Embolic coils may take the form of helically wound coils, randomly wound coils, coils wound within other coils, or many other coil configurations. These coils are generally formed of radiopaque metallic materials, such as platinum, gold, and tungsten, or alloys of these metals. Often times, several coils are placed at a given location in order to occlude the flow of blood through the vessel.
One example of an embolic coil design is disclosed in U.S. Pat. No. 6,179,857 entitled, “Stretch Resistant Embolic Coil with Variable Stiffness.” The coil is a helically wound coil in which various combinations of adjacent turns are spot welded together to create a stretch resistant coil of a preselected flexibility. Another coil configuration is disclosed in U.S. Pat. No. 6,183,491 entitled, “Embolic Coil Deployment System with Improved Embolic Coil” which shows an embolic coil having a relatively flexible proximal portion which resists stretching.
Also, U.S. Pat. No. 5,853,418 entitled “Stretch Resistant Vaso-occlusive Coils,” discloses a helically wound coil having a polymeric stretch resistant member extending through the lumen of the coil and fixedly attached to both the distal end and the proximal end of the coil. Other examples of coil configurations are disclosed in U.S. Pat. No. 5,334,210, entitled, “Vascular Occlusion Assembly” and U.S. Pat. No. 5,382,259 entitled, “Vaso-occlusion Coil With Attached Tubular Woven Or Braided Fibrous Coverings”. With all coil designs, it is important that embolic coils remain very flexible for traveling through vessels when used with catheter deployment systems.
A variety of deployment systems are available for placing embolic coils within an aneurysm or vessel. An example of such a system is disclosed in U.S. Pat. No. 6,113,622 entitled, “Embolic Coil Hydraulic Deployment System,” assigned to the same assignee as the present patent application. The hydraulic embolic coil deployment system uses fluid pressure which is applied to the lumen of the deployment catheter for expanding the distal section radially to release the embolic coil at a preselected position.
Another coil deployment system utilizes a deployment catheter having a socket at the distal end for retaining a ball which is bonded to the proximal end of the coil. The ball is placed in the socket within the lumen at the distal end of the deployment catheter, and the deployment system is then moved into a vessel to place the coil at a desired position. Then, a pusher wire with a piston at the end is pushed distally from the proximal end of the deployment catheter to thereby push the ball out of the socket and release the coil at the desired position. This system is disclosed in U.S. Pat. No. 5,350,397 entitled, “Axially Detachable Embolic Coil Assembly.”
Also, U.S. Pat. No. 5,263,964 entitled, “Coaxial Traction Detachment Apparatus and Method” discloses another coil deployment system. This system uses glue or solder for attaching an embolic coil to a guidewire which is, in turn, placed within a flexible deployment catheter for positioning the coil within the vessel at a preselected position. Once the coil is at the desired position, the coil is restrained by the deployment catheter, and the guidewire is pulled from the proximal end of the deployment catheter causing the coil to be detached from the guidewire and released from the deployment system.
Additionally, a small diameter vasoocclusive coil deployment system is disclosed in U.S. patent application Ser. No. 09/580,684 entitled, “Small Diameter Embolic Coil Hydraulic Deployment System,” filed on May 30, 2000 and assigned to the same assignee as the present patent application. In this system, the distal end of a cylindrical headpiece is inserted into and bonded with an embolic coil. The proximal end of the cylindrical headpiece has a diameter approximately equal to the diameter of a lumen of a deployment catheter allowing the proximal end of the cylindrical headpiece to be disposed in fluid-tight engagement within the lumen of the distal section of the deployment catheter. When fluid pressure is applied to the lumen of the deployment catheter, the wall of the distal section of the deployment catheter expands radially and releases the cylindrical headpiece along with the embolic coil.
Examples of other deployment systems are disclosed in U.S. Pat. No. 5,122,136 entitled, “Endovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas” and U.S. Pat. No. 5,108,407 entitled, “Method And Apparatus For Placement Of An Embolic Coil.”